A genetic approach to the analysis of the cell cycle in Caulobacter crescentus is proposed. These gram negative bacteria divide unequally to give two daughter cells with different developmental pathways: a motile swarmer cell which develops into a new non-motile stalked cell, and a stalked cell which elongates and divides continuously to produce new swarmer cells from one pole. Conditional mutations that affect specific developmental steps in each of these two pathways will be isolated and characterized. From the phenotypes of these mutants it should be possible to deduce the genetic organization of different developmental pathways. They will also offer substrates for biochemical studies now underway on development. The second major part of the proposed project is the development of a genetic system for mapping and complementation. Polarized inheritance of markers in C. crescentus has been demonstrated (Newton & Allebach, 1975) and there is strong reason to believe that a sexual mechanism is involved in gene transfer. Conjugation in these bacteria will allow the construction of a genetic map and the isolation of episomes. These techniques will be used in the genetic characterization of the conditional developmental mutants.